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    Control of Listeria monocytogenes contamination in fresh beef by using lactococcin BZ
    (Wiley, 2017) Yildirim, Zeliha; Yerlikaya, Sabire; Oncul, Nilgun
    The aim of this study was to investigate the inhibitory effect of lactococcin BZ produced by Lactococcus lactis spp. lactis BZ against Listeria monocytogenes in raw beef. Lactococcin BZ depending on concentration (400-3,200 AU/ml) reduced the counts of L. monocytogenes attached to meat surface (from 4.71 log CFU/g to undetectable level, and from 7.92 to 3.64 log CFU/g) in 5 min. When meat samples were simultaneously inoculated with lactococcin BZ and L. monocytogenes, lactococcin BZ reduced the count of non-attached Listeria cells in 5 min by 1.58-5.03 (undetectable level) log cycles in the low inoculum (5.03 log CFU/g) and 1.11-5.58 log cycles in the large inoculum (7.86 log CFU/g) compared to control samples. Also, lactococcin BZ at 400-3,200 AU/ml reduced the number of L. monocytogenes in meat samples inoculated at 2.45, 4.42, and 7.29 log CFU/g throughout 12 day storage at 4 degrees C and maintained its biological activity. In addition, lactococcin BZ adsorbed to meat surface and adsorption did not adversely affected antilisterial activity. Practical applicationsIn this study, we investigated the inhibitory effect of lactococcin BZ produced by Lactococcus lactis spp. lactis BZ against Listeria monocytogenes during, after or before attachment on raw beef. It was observed that lactococcin BZ depending on its concentration (400-3,200 AU/ml) and amount level of Listeria cells (4.71 or 7.92 log CFU/g) reduced the cell counts of L. monocytogenes in the meat samples very effectively. Lactococcin BZ at 1,600 and 3,200 AU/ml showed strong antilisterial activity toward L. monocytogenes before, during and after attachment to meat samples, but its antilisterial activity was higher before or during attachment than after attachment. Therefore, lactococcin BZ could be potential alternatives to chemical preservatives for meat industry.
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    Inhibitory Effect of Lactococcin BZ Against Listeria innocua and Indigenous Microbiota of Fresh Beef
    (FACULTY FOOD TECHNOLOGY BIOTECHNOLOGY, 2016) Yildirim, Zeliha; Yerlikaya, Sabire; Oncul, Nilgun; Sakin, Tuba
    In this study, the effect of lactococcin BZ on microbiological quality of fresh beef is investigated. For this purpose, the meat samples were treated with various amounts of lactococcin BZ (200-2500 AU/mL), a bacteriocin produced by Lactococcus lactis spp. lactis BZ, and kept at 4-5 degrees C for 12 days. During storage, the microbiological properties of the meat samples with or without lactococcin BZ were determined. Inhibitory effect of lactococcin BZ depended on its amount. The higher the amount of lactococcin BZ, the higher the inhibitory activity. Treatment with lactococcin BZ at the level of 2500 AU/mL resulted in 4.87, 3.50 and 3.94 log cycle decrease in the counts of mesophilic, psychrotrophic and lactic acid bacteria, respectively, and 1.90.10(4) and 1.04.10(2) CFU/g reduction in conform and faecal conform bacteria, respectively, at the end of storage as compared to their initial numbers in the control sample. However, the counts of these bacteria in control samples increased during storage. Also, lactococcin BZ at 1600 AU/mL showed very strong antilisterial effect against Listeria innocua in fresh meat and reduced the cell numbers from 6.04 log CFU/g to undetectable level on the 6th day of storage. In conclusion, lactococcin BZ has a potential use as a biopreservation agent to improve safety and shelf life of raw beef.